Japanese Patent Application Laid-Open Publication No. 2011-184895 (hereinafter referred to as “the relevant patent literature”), for example, discloses a smart entry system which is constructed to inform of an operating state of an auto lock function, and which can inform, by means of a vehicle buzzer (beep) and a vehicle indicator, a passenger that the vehicle has shifted to an auto lock mode. When a predetermined condition for locking vehicle doors has been established, the smart entry system disclosed in the relevant patent literature sounds the vehicle buzzer and changes a display of the vehicle indicator so that the passenger present outside the vehicle can recognize an operating state of the auto lock function.
According to the disclosure of the relevant patent literature, the vehicle buzzer sounds once and the vehicle indicator is illuminated in green color, for example, once the predetermined condition for locking the vehicle doors is established and the vehicle shifts to the auto lock mode. The vehicle buzzer sounds two times and the vehicle indicator turns off, for example, once the auto lock function is executed to close the vehicle doors. By the sounding of the vehicle buzzer and the changed display of the vehicle indicator, the passenger can recognize the operating state of the auto lock function.
Namely, with the smart entry system disclosed in the relevant patent literature, the passenger can recognize the operating state of the auto lock function auditorily through the sounding of the vehicle buzzer and visually through the display of the vehicle indicator. However, the passenger may sometimes be unable to hear the sounding of the vehicle buzzer in places where ambient noise sound is too great. Also, the passenger may sometimes be unable to recognize the illumination of the vehicle indicator in too light places. Further, it tends to be difficult for the passenger to recognize the illumination of the vehicle indicator when the passenger is considerably away from the vehicle. Thus, with the smart entry system disclosed in the relevant patent literature, there may occur a situation where the passenger is unable to recognize the operating state of the auto lock function even when the operating state is informed to the passenger. In such a case, the passenger may undesirably leave the vehicle with the doors left unlocked without the passenger noticing that the doors have not been locked.